1. Field
This disclosure relates generally to non-volatile memories, and more specifically, to phase change memories.
2. Related Art
Phase change memories (PCMs) have advantages over other non-volatile memories (NVMs) such as high endurance, high density and low voltage operation. There are many challenges, however, for production in large quantity. The device structure should allow for consistently being able to change the state of a cell while also having good data retention. Data retention can be a problem if the phase change material is not completely placed in the amorphous condition. If there is any crystalline material left after converting to the amorphous state, the remaining crystalline material can act as a seed for further crystalline growth. Over time, especially in the presence of heat, the phase change material can convert to the crystalline phase and thus lose its logic state. Also there must be a corresponding process that can reliably achieve the desired device structure. Although the process for making PCM devices is potentially simpler than for typical NVM devices, the process must be able to consistently provide the desired structure without creating reliability problems for the PCM device.
Thus there is a need for a PCM structure that meets the desired characteristics and a process for achieving the desired PCM structure that improves on one or more of issues pointed out above.